Dehydrating apparatus



Feb. l2, 1929. Y H. S. MaCKAYE DEHYDRATING APPARATUS Filed Dec. 31; 1925 3 Sheets-Sheet l :lil/

Feb. 12, 1929. 1,701,813

H. s. MacKAYE DEHYDRATING APPARATUS Filed Dec. 5l, 1925 Y 3 Sheets-Sheet 2 Umbauten Feb. 12, 1929.

H. s. MaoKAYE DEHYDRATING APPARATUS 5 Sheets-Sheetl Filed Deo. 3l, 1925 fig. Jj

llatentecl Feb. 12,

UN-IIT'ED sT'ATEs PA'li-grrrv .1,101,813 OFFICE;

HAROLD S.. MACKAYE, OF YONKERS, 4NEW YORK, ASSIGNOR, BY MESNE ASSIGNIIIENTS,

T DRY FRESH-PROCESS, INC., .A

CORPORATION 0F NEW' JERSEY.

DEHYDRATING APPARATUS.

, Application mea' December 31, 1925;y serial No. 78,679. y

Thel presentinvention. relates to a novel and improved process for ythe dehydration of fruits, vegetables etc.` in a manner to permit satisfactory restoration of their 5 original condition, by steeping in water; as- Well as `to a novelapparatus. for carrying :ut said process. l Inl order to Iprevent the discoloration o." other objectionable alteration of. certain lo fruit and vegetables, they-should be ydehyvdrated in an atmosphere as free vfrom oXy "Vgen as possible, at least in the early stages of thefprocess.4 It has also been found that during these earlier stages, the atmosphere to which the product is subjected should be fairly moist, thus preventing case hardeu-l ing7 and "rupture of the delicate cells.

The process of Vdel'iydration' as` usually practiced calls for al suitable heating of the product While causing a current of moisture-absorbing gas to pass overv and around the product. Even where great care is eX- ercised, it isvirtually impossible to so pack some kinds of materials to be dehydrated that a substantially equal resistance will be opposed to flow of the gas in the dilferent trays containing thematerial. Accordingly it is desirable that means be supplied for governing the rate of flow, and consequently accordance with temperature indications existing from tn nelto time.v Y t l The present invention provldes for carrying .out the. requirements incident to theabove conditions, and also presents otherpad` vantages hereinafter pointed out.

The invention is illustratedin certain pre; fcrred embodiments, shown by way of eX-, ample, in the accompanying drawings, f wherein Figureql .is a 'vertical section of my apparatus on theline 1?'-1 in Figure 2,.Fig

, ure-2is asimilar sectional view on the line 2--2 in-'Figuray '1, Figure 3 is an-s' enlarged horizontal'sectional View of one sideon the -line in Figure2, Figureelv isanen'd view'of the apparatua'andfFigure 5' is -a y transverse vertical section` of a modified form of the device, The drawings are diagrammatic in character, and minor details of an obvious and well known naturefar'e i omitted for the sake of clearness.

. the temperature, in each tray separately, inf

of thev particles the tray. Any form-of trayyor container known to be suitable for puilposes of dehydration may of course, be use A The containers 10 are'supported iniany suitable manner between lhorizontal partitions 11, being introduced through doors 12 at the front or back or both, if desired. The containers are placed in auniformlfy slanting position as shown in'Figure 2, and 65 the partitions 11 are correspondingly placed,

being located so as to leave a circulation space above and below each container.

Atone side of the preferred device, vertical vplates or partitions 13 ldepend from the edges of the'partitions 11, to form ilues 14 extending down to the Inain'horizontal` -entrance iuel. From the opposite edges of the partitions 11,-vertical 'plates or par-4 titions 16 rise to form, the iues 17 which 75 extend to the main upper horizontal flue 18.

All ofthe partitions and plates '11, 13 and 16 'extendlirom one'end to the other` of the main outer casing 19, or from left to`rig`ht in Figure 1. My invention may be successfully carried out for some purposes, and, so far as 'reversal' of gas currents is concerned, even lwhere the partitions 13 and 16 are omitted. Y

i At one, side of the. apparatus, between the outermost partiti-on 13 and the main casing' 19, a rising flue 20 extends from on en d off the mainentrance flue 15 to theexlt flll'e or chimney 21, justI below which this rising'A fiue20 joins the exit end Ioi the upper cross flue 18. L At this pointy a damper 22 orequivalent means is provided, whereby 'the'.open-- ingslfrom the respectiveflues 18 and 20to the exit-21 may be controlled. As shown, the Vdamper closes Hue 20 and'leaves 18 open.

-At the opposite side :oflthe rapparatus, afseeond rising Hue 23 extends from one end of the upper crossV flue 18, down past the entrancexto" the/crossV flue" 15, to the endi of what may be calledvthe' su ply ue 24. 10o This flue runs parallelto the ue 15, andjis bounded above and below respectively' by the horizontal partitions 25 and 26.

The material tobedehydrated is disposed ,is just below. the4 right hand wall of the in any welllknown lmanner within shallow' trays 10, which are preferablyimade of wirel`v mesh, as coarse as, 1s ,consistent with the" sizev flue 23. lThis partition is-fpreerably made double with insulating material suchraslasbestostorv the like between thevupper-:andf .116,

lower plates, to prevent so far as possible undue heating from below by-direct radiation. I also prefer to use an insulating layer over the top of the flue 15 as shown at 27, for the same reason.

vThe partition 26 is preferably a shallow water pan, which may be supplied with water through the entrance 28, or otherwise.

This extends from directly under the fluel 23 toward the right in Figure 2, far enough to lea-ve an adequate opening into the liue 24 from the mixing flue 29.

All of the flues above described extend horizontally from end to end of the apparatus, by which is meant from right to left in Figure 1.

The heated gases employed in dehydration are products of a combustion which is kept as nearly perfect as possible, in order to unite as large a proportion of oxygen as possible with the carbon and hydrogen of the fuel preferably as OO2 and H2O (gas). Moreover,.it is highly desirable, in order to attain uniform and reliable performance, to supply the heated gases in equal quantities from end to end-or from the left to the right of the advancingl current.

The above ends may be attained by burning oil or gas all along under the apparatus from one end to the other, as, for instance, by means of the gas pipe 30, having small openings at close intervals to produce burning gas jets which may be raised or lowered at will in any well known manner as bythe valve 30l (see Figure 1). An opening 31 in the casing (see Figure 2) supplies the necessary air.

In order that the material may be uniformly treated, it is best to insure a thorough mixture of the gases that pass away from the point of combustion. Otherwise some of the unburned air, being very hot, becomes a detrimental oxidizing agent.

To accomplish this thorough commingling of the gases, I prefer to provide within the mixing iiue 29 means for agitating the gases automatically as they travel forward under the influence of natural draft. One means that is found effective for this purpose comprises a series of oppositely sloping baffle plates 32, arranged as shown in Figure 2, and extending from end to end of the flue, that is from right to left in Figure 1.

It has been found by experience that stationary dehydrators depending upon connection or natural draft are often subject to two annoying disadvantages. One of these is a tendency to overheating in one or the other of the lower trays; which arises from their receiving an undue supply of heat by direct radiation from the inconiing hot gases, before they divide to pass through the passages wherein the trays are located. To obviate this I employ the insulating partitions 25 and 27, one or both.

to heat the Water in the pan 26.

The vsecond disadvantage is found in the tendency of the material to dry faster, and even sometimesto Scorch, on that side of each tray whore the hot gases are introduced than on the opposite, or outgoing, side of the tray. This disadvantage I overcome by providing means whereby the direction of travel of the gases may be reversed as frequently as desired. That is to say, the opposite sides oredges of each tray become incoming and outcoming sides in alternation. This contributes very materially to the uniformity of the results. lVhile this feature is not essential to my invention, and is not shown in Figure 5 it is present in the more elaborate and perfected embodiment of the invention shown in' Figures 1 to 4.

'lhe reversal of gas currents is controlled by two dampers, in the speciic form shown. One of these, already described, is the damper 22. The other is a similar damper 33, which in the position shown in Figure- 2 closes communication from the flue 24 to the flue 23, and in the dotted'line position shown in that figure, closes communication from 24 to 15, leaving access open to the flue 23.

One mode of operation may now be described. The material, properly distributed on the trays 10. having been introduced through doors 12, these are closed, and the gas is lighted at 30, the dampers 22 and 325 being in the positions shown in Figure 2.

The hot gases passing from the jets il() are thoroughly mixed in the flue 29, and act Thus the gases take up moisture they pass back over the pan 26 within the flue 24. These moist hot gases then pass by the main entrance flue 15 to the flues 14, by which the current is divided so that each tray 10 is surrounded by a separate gas stream. The gases pass partly over and under and partly through the layer of material in each tray, and thence by the fiues 17 to the horizontal iue 18, which conducts them to the exit flue 21.

After a suitable interval, depending upon the nature and condition of the material treated, the dampers 22 and 33 are moved io the dotted line positions, whereupon the gases will pass first up the flue 23, then down the iues 17, over, under and downward through the material in the trays, then through the flues 14 and out through tlues 20 and 21. It will be seenthat this not only reverses the direction of the currents across the material but also through it,from up- .ward to downward.

This alternation of current direction may be repeated as often as desired, and insures uniformity of results at the entrance and exit sides ofthe trays.

Inasmuch /as the distribution of the gas currents through and around the respective trays depends to some extent upon the naloo llU

ture and distribution of the material on the :respective trays, uniform gas distribution cannot be'successfully attained once for all4 by the original constructionI of the apparatus. l=For this reason Ihaveprovided an entirely separate( passage from the common .ilue 15 (or 18) to the common outlet Hue .1

(or 15) for each tray.

Now, as soon as operation is begun, the temperature conditionsin each passage may e kept under observation by appropriate /useof electrotliermic or other thermometers, and the separate individual dampers 34 may Jbe so set that uniform results are attained.` It is to be understood that the moistening of the gases will ordinarily be only necessary during the earlier stages of the process. The length of time during which this moistening is continued is regulated by thej amount of water that is supplied to the.

pan26.

.My perfected apparatus as shown in Figures l to 4 lends itself to carrying out a novel mode of treatment of the material, which is one-of the features of my invenf tion. This mode 01 process involvesga novel step employed alone at the beginning of the treatment or repeated in alternation with other steps.

The novel step or operation in question may be termed closed heating, and may be carried out in the specific apparatus shown by placing each of the dampers 22 and 33 in the half-Way or forty-five degree position, whereby t-he current issuing vfrom` the flue 24 is divided about equally. between the 'lues 23 and 18 on the one hand and the lues 15 and J20 on the other hand. If desired the dempers 34 may be closed, as well. the passages containing the trays 10 have been lled as far as possible with gases weak .f in oxygen. I prefer to accomplish this by merely-'warm gases.

setting one or the other of the dampers 22, 33-more or less out of the `mean or fort five degree position, thus permitting a slig t balance of draft-inducing pressureA one Way or the other, to cause slow passage of the This prevents prelim- .inary overheating. Indeed any period of closed heating may bey carried out in this manner, and this expression as used in my claims is not intended to apply only to the use of perfectly still air or gas around the trays. With the apparatus in this condition, the .products of combustion pass all around the flues and ducts containing the material to be treated, and therefis a slow i'drying without draft. The moisture of the material itselflis thus kept in contact with fthel material, so as to prevent case hardening, and little orfno Water is necessary in the pan 26. t One important result of the use of this .e1 osed heating, when alternated with the It is best to employ this step after i active useof gas currents over the material 'l in the ordinary vmanner .is found in the economy of fuel; andi thisv without any loss of time or impairment of results.

The heated .gas currents ordinarily used have a double function. They warm thefpart ofthe moisture extraction by closed heating at a low temperature withv the material in contact Withits own moisture;

relatively short time in active heating by contactl with a rapid draft of hot gases which sweep away the moisture. ter need only occupy a very small space ot' time, so that the material has notftime to be detrimentally affected by the high temperature. l

Furthermore,l this process economizes fuel,

1geous therefore to accomplishl the greater )while using the higher temperature fora This lati' because during the intervals of closed heat- Aing, the gasA or oil flame may be turned low, and only be raised during the short intervals of rapid convection for sweeping out purposes.

each flue is asmfollows.

Assuming the dampers 22 .and 33 to be set as shown in Figure 2, the gas is turned low. The dampers 34 are then all closed but one. The. low-turned gas will produce plenty oi' heat for rapid convection to sweep out one tray-passage at a time, and, while this is going on, the material in the other Another way of getting this same result` of alternate closed and open heating in tray passages is undergoing closed heating.'

By thus opening each passage in succession (keeping the others closed) andrepeating the process as long' as desired, the necessary alternation of closed and open heating may be carried on Without turning the gas upv and down. Of course this'turning up and down of .the Agas is not essential in vany case, but, Where Jthe iirst above described variant of my process is employed, it is desirable to save-time. vf

The reversal of current is not so important, where closed and open heating are used in alternation, but it may be emplo ed with advantage, even in this case. en so employed, lit will be found well to reverse thecurrent direction after each closed heating interval.

My invention is not Icessarily embodied in a reversible device, and I have shown 'a modification containing some of the features of the invention in Figure 5.

In this form the heat is supplied by a long wick 35, running the entire length of the device, and drawing oil from the reservoir 36; although of course gas may` be here used if desired.

The gases'pass under and around-the water pan 26, and separate currents are carried by the inclined iiues 37 to the respective tray containing ducts 38, which in this case are inclined7 so that the gases pass entirely through the layers of material in the trays. From the ducts 38 the gases are led separately through the flues 39 to the exit Chim ney 21. The damper-s 40 make it possible to accomplish individual current control in the. separate tray-containing passages, for the purposes alreadyA described.

To prevent undue heating by direct radiation, insulation 41 is placed yover and around the ues that lead the gases to the entrance flues 37.

My invention may be embodied in a. great variety of forms, and by a number of varie ants of the process, by'changes that will be obvious t0 those skilled in the art. I do not wish to be limited to the details herein shown and described.

What I claim is- 1. Dehydrating apparatus comprising a Agroup of ducts adapted to receive containers for moist material, means for producing and directing a current of' hot gases under and through said group, and a layer of heat insulating material under said group adapted to shield the lower ducts from direct heat radiation.

2. Dehydrating apparatus comprising a group of ducts adapted to receive containers for moist material, a waterlpan partition below the same, a heat insulating partition between said group and said water pan, and means for causing a currentof hot gases around said water pan and said insulating partition successively and then through said ducts.

3. Dehydrating apparatus, comprising means for supporting and enclosing the material to be treated, a source of hot products of combustion, a mixing duct for leading the productsofcombustion to the material to be treated, and agitating means Within sald duct adapted to direct the current of gases alternately up and down.

4. Apparatus as in claim 3, wherein the agita-ting means comprise a series of inclined bafile plates. c

5. Apparatus as in claim 3 Wlierein one side of the lmixing duct is a water pan.

6. Dehydrating apparatus comprising a group of mutually separated drying ducts, means for supplying drying gases thereto, means for leading said gases away therefrom, and means adapted to cause the gases from the supplying means to move either through said ducts or around the group of ducts at will.

7. Apparatus as in claim 6 in combination with a separate valve for each duct adapted to vary the resistance thereof to the passage of gas therethrough.

8. Dehydrating apparatus comprising a group of ducts for supplying drying gases, means for conveying said gases above, below and on two sides of said group, and means for controlling the passage of gases through said group of ducts.

9. Dehydrating apparatus comprising a group of ducts adapted to receive containers for moist material, an exit flue, a source of hot gases, passages leading around said group of ducts to said exit fiue, and separate means ,for controlling admission of gases from said passages to each of said ducts.

10. The-process of dehydrating food material for making the same tit for restoration by adding wateiywhich consists in subjecting the material to treatment involving preparatory heating in a relatively still drying atmosphere followed by the use of an active current of hot gases passing the material.

1l. The process of dehydration which consists in; subjecting mois-t material to radiant fheat in a relatively still drying atmosphere and to convective heating in an active current of hot gases, in alternation.

In testimony whereof I hereto affix my signature this 30th of December, 1925.

HAROLD S. MACKAYE. 

